Estimate conductor size from load, distance, and voltage. Review ampacity, losses, resistance, and standard sizes. Create cleaner installations with practical graphs, tables, and downloads.
| System | Material | Voltage | Current | Length | Allowed Drop | Typical Result |
|---|---|---|---|---|---|---|
| DC | Copper | 12 V | 10 A | 5 m | 3% | 6 mm² |
| DC | Copper | 24 V | 15 A | 8 m | 3% | 6 mm² |
| Single-Phase AC | Copper | 230 V | 16 A | 30 m | 3% | 2.5 mm² |
| Three-Phase AC | Aluminum | 400 V | 32 A | 40 m | 3% | 10 mm² |
This calculator combines voltage-drop sizing and ampacity sizing, then recommends the larger standard conductor size.
1) Current from power DC: I = P / (V × η) Single-phase: I = P / (V × PF × η) Three-phase: I = P / (√3 × V × PF × η) 2) Design current I_design = I_base × (1 + safety margin) × (1 + future expansion) 3) Required ampacity Ampacity_required = I_design / (temperature factor × bundling factor) 4) Voltage-drop sizing area A = (ρ × K × L × I_design) / V_drop Where: A = conductor area in mm² ρ = resistivity in Ω·mm²/m K = 2 for DC and single-phase, √3 for three-phase L = one-way length in meters V_drop = allowed voltage drop in volts 5) Actual drop check DC / Single-phase: V_actual = 2 × I_design × R_conductor Three-phase: V_actual = √3 × I_design × R_conductor R_conductor = (ρ × L) / A
The recommendation is the larger of the minimum size needed for voltage drop and the minimum size needed for derated ampacity.
Step 1: Select current mode if you already know amperes. Select power mode if you know watts.
Step 2: Choose DC, single-phase AC, or three-phase AC. Enter system voltage and conductor material.
Step 3: Enter one-way cable length. Then set your allowed voltage drop percentage.
Step 4: Add safety margin, future expansion, and any derating factors for temperature or grouped cables.
Step 5: Press calculate. The result section appears below the header and above the form.
Step 6: Review the selected size, voltage drop, ampacity, loss estimate, chart, and exported report options.
Low voltage systems lose a higher percentage of their source voltage across the same resistance. A small resistance that seems harmless at 230 V can become a serious drop at 12 V or 24 V, so larger wire sizes are commonly required.
Enter one-way length. The calculator internally applies the correct path factor: twice the length for DC and single-phase circuits, or √3 behavior for three-phase voltage-drop estimation.
Aluminum has higher resistivity and usually lower reference ampacity for the same cross-sectional area. Because of that, aluminum conductors often need a larger size than copper for identical load and voltage-drop limits.
These fields help you size beyond today’s exact load. They can reduce overheating risk, handle startup variation better, and leave room for later equipment growth without immediately replacing the conductor.
A conductor that looks acceptable in free air may run hotter in warm locations or grouped bundles. Derating factors adjust the usable ampacity downward so the selected size remains more realistic for actual installation conditions.
No. This is an engineering estimate tool. Final wire selection must match local electrical code, insulation temperature rating, installation method, fault protection, termination ratings, and any project-specific design standard.
Both matter. Voltage drop controls performance, while ampacity controls conductor heating. This calculator checks both and recommends the larger standard size, which is a practical approach for many low voltage design tasks.
Yes, it is useful for many low voltage applications where length, current, and drop are important. Still verify equipment manufacturer limits, especially for batteries, electronics, motors, and communication systems.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.